Fix coverity warn and make agetn return 0 in case of fail (instead of ut64_max)
Fix coverity warn and make agetn return 0 in case of fail (instead of ut64_max)

Maijin/sdb,alvarofe/sdb,Maijin/sdb,Maijin/sdb,pombredanne/sdb,alvarofe/sdb,pombredanne/sdb,radare/sdb,pombredanne/sdb,pombredanne/sdb,alvarofe/sdb,pombredanne/sdb,Maijin/sdb,radare/sdb,alvarofe/sdb,alvarofe/sdb,pombredanne/sdb,alvarofe/sdb,alvarofe/sdb,radare/sdb,radare/sdb,pombredanne/sdb,Maijin/sdb,Maijin/sdb,alvarofe/sdb,radare/sdb,Maijin/sdb,pombredanne/sdb,Maijin/sdb,alvarofe/sdb,alvarofe/sdb,pombredanne/sdb,Maijin/sdb,pombredanne/sdb,Maijin/sdb,radare/sdb,Maijin/sdb,radare/sdb,radare/sdb,pombredanne/sdb,radare/sdb,alvarofe/sdb,radare/sdb,radare/sdb